My left grip has stopped working. I checked the wiring and it is all still connected. I guess my next step is to cut the entire wire off at the grip and re-wire it with different wire as there has to be a break in it somewhere

Have a volt/ohm meter? Check the resistance on the grip. You'll have to separate the grip wiring from the switch before checking so you don't pick up the resistance from the good grip. Check at the switch end of the wire as well as right where the wires come out of the grip. If you get an open reading at the switch end of the wires but resistance at the grip, the grip is good but the wiring is bad. If open reading both locations, the grip is bad.